The present invention relates to optical modules and in particular, to an optical module for use in high bit rate applications comprising an optically transparent carrier mechanically attached and electrically connected to a carrier substrate connectable to a circuit carrier.
Optical interconnects became in recent years widely used in electronic devices due to their capability of supporting a much higher bandwidth than traditional cable interconnections. In this context, the development of optical modules for converting optical signals into electrical signals and vice-versa plays a crucial role in a wide range of applications, such as midboard applications, using optical interconnects.
Common optical modules are realized by an optically transparent carrier assembly including various optical elements. An example of a known optical module is illustrated in FIG. 15. The optical module 2100 includes a carrier 2110 optically transparent to a defined wavelength, on top of which optical elements such as optical receivers and transmitters 2120 as well as various integrated circuits 2130 are mounted. The optical transmitters and receivers 2120 and the integrated circuits 2130 are connected to connection terminals 2103 arranged on a surface of the transparent carrier 2110 by means of connecting traces 2112. In applications currently on the market, the optically transparent carrier assembly 2100 is connected to a circuit carrier, such as a printed circuit board or a connector socket, for instance by soldering the transparent carrier 2110 to the circuit carrier.
In present applications the optical module 2100 can be designed to be mounted on a circuit carrier. In such a configuration, the active optical elements will emit light through the optically transparent carrier 2110 towards a direction opposing the circuit carrier. The light will be focused and redirected by means of an optical coupling element, which is normally arranged on top of the optically transparent carrier so as to align a lens with the optical elements 2120. In this kind of applications, there is an opening in the circuit carrier through which the heat is dissipated by means of a thermal bridge (not shown) in order to transfer the heat generated by integrated circuits and optical elements.
An arrangement in which the optical module is directly connected to a circuit carrier 2200 by soldering electrical connection terminals on the optically transparent carrier 2110 and electrical connection terminals on the circuit carrier 2200 is shown in FIG. 16. Further, the optical module 2100 and the printed circuit board 2200 can be assembled into a module casing 2500. This arrangement is illustrated in FIG. 17. The casing 2500 acts as a primary heat sink by the arrangement of the thermal bridge.
Although the module described in FIGS. 15 to 17 is quite compact, according to this design the transparent carrier mounting the optical elements 2120 is directly mounted on the circuit carrier 2200 and therefore can be only used in applications where the circuit carrier 2200 is designed so that the casing 2500 can act as heat sink. Moreover, according to the existing design, the transparent carrier 2110 is generally fixed on the circuit carrier 2200 by means of solder bumps or adhesive attach, since any other fixing design such as a by means clamping element or the like may damage the transparent carrier 2110 mounting the optical elements 2120. Therefore, the optical module 2100 can only be used in application whose mechanical connection requirements can be satisfied by a solder bump or adhesive connection.
However, different applications using optical modules may have very different requirements concerning the generated heat, the thermal dissipation, mechanical and/or electrical connection, direction of light and the like. Moreover, some applications may need an optical module where the optical interface is fixed, while other applications may require an optical module with a detachable optical interface. Finally, it may be advantageous to have an optical module adapted to be mounted on a circuit carrier, such as a printed circuit board, according to different fixing designs, such that the same optical module can be used in different applications using different mounting schemes.
The underlying problem addressed by the present invention is therefore to provide a miniaturized optical module capable of being mounted on a circuit carrier, which is robust and assures reliable mechanical, electrical and optical connections with the circuit carrier and which can operate in a variety of applications having different requirements regarding optical, electrical, thermal and mechanical connections.